1. Field of the Invention
This invention is directed to optical signal processing systems, in general, and to the photo-diode array which is used as the output section, in particular. More particularly, an improved photo-diode array with expanded dynamic range is provided.
2. Prior Art
There are many types of optical signal processing systems known in the art. One such system is described in copending application entitled ACOUSTO-OPTIC R-F FILTER WHICH IS TUNABLE AND HAS ADJUSTABLE BANDWIDTH, by J. H. LABRUM, bearing U.S. application Ser. No. 566,437, filed on Dec. 28, 1983, and assigned to the common assignee. This particular copending application is not intended to be an exhaustive study of optical signal processing systems but is one illustrative representation thereof.
In the known systems of this type, one of the limiting factors on the operational characteristics thereof is the output portion of the system. In the known prior art, the output section usually includes a photo-diode array which is used to detect the optical signal produced by the remainder of the system and to supply representative electrical signals to output signal controlling and/or processing circuitry.
In the past, it has generally been desirable to have a dynamic range which is as wide as possible. The goal has, typically, been to permit operation on the order of a 60 dB dynamic range. However, in the past the typical operational range which has been achievable has been on the order of 30 dB instantaneous dynamic range. Often times, the limiting factor in this operation has been the dynamic range of the output electronics which has the 30 dB characteristic. That is, the photo-diode array has frequently been limited to a dynamic range on the order of approximately 30 to 40 dB. However, the satisfactory operational characteristics of the photo-diode array have not been able to be utilized because of the output circuitry limitations. Consequently, an improved output system is highly desirable.